[1] How did life begin?
The correct answer is "whilst we do not know for certain the answer to this question, we have a large body of experimental evidence pointing to relevant testable natural mechanisms, that have been demonstrated repeatedly to work in the laboratory". The testable natural mechanisms in question being chemical reactions. It is perfectly reasonable to postulate chemical reactions as the basis for the origin of life, because living organisms today are manifestly reliant upon chemistry for their functioning, and the body of evidence for this is overwhelming. Scientists have elucidated in exquisite detail a whole range of metabolic pathways, ranging from the utilisation of glucose to produce energy in metazoan cells, through the chemistry of photosynthesis in plants, to the mechanisms extant for the synthesis of DNA itself. Indeed, so vast is the extant body of literature presenting the relevant empirical elucidation of these chemical reactions, that it would take several dozen lifetimes for a human being to read them all. Consequently, since we have a vast body of evidence to the effect that life is chemistry writ large, it makes eminent sense to postulate a chemical origin thereof.
[2] Is any form of life really simple?
In order to answer this, one needs to have in place a proper, rigorous metric defining what is meant by "simple", and conversely, what is meant by "complex". Without such a metric, the question is meaningless.
However, light is once again being shone upon this question by relevant laboratory research. Scientists are now in the position to plan and execute experiments focusing upon the properties of model protocells, of the sort that are hypothesised to have been formed 3.5 billion years ago. These model protocells are considered to be "simple" in the sense that they are composed of a minimal set of constituents, namely a single strand of RNA, encapsulated within a lipid vesicle. How these model protocells behave, and whether it is possible for such protocells to acquire additional features via evolutionary processes, will constitute a major area of study for abiogenesis researchers in the future.
Indeed, much of the previous research in the field of naturalistic abiogenesis centred upon the establishment of a rigorous basis for the appearance of the building blocks needed for said protocells, and the empirical demonstration that relevant molecules were not only capable of self-assembly, but did so quite naturally under relevant conditions. The cutting edge of research is now moving toward determining how the first protocells were likely to behave, based upon the notion that the models being constructed in the laboratory are reasonable models for those past protocells. Should those models produce the relevant empirical results, namely, that the relevant experiments demonstrate that such minimal model protocells can indeed acquire additional features, and that those features bear appropriate relationships with key features seen in modern cells, then those who wish, for ideological reasons, to dismiss testable natural processes as being capable of producing the biosphere from simple chemical antecedents, will find life much harder.
[3] Where did the instructions come from?
This is a deliberately loaded question that presupposes its purported "answer". The simple fact is, that whilst the chemical reactions that are associated with genetics and the inheritance of traits, bear the appearance of "instructions", carrying this analogy too far is misleading. Not least, because it has been determined by numerous researchers and their empirical work, that the so-called "genetic code" is itself an evolvable entity. Indeed, numerous papers on this subject exist, illuminating our understanding of the origin of the genetic code, and all serious researchers consider that body of work to be sound and robust.
[4] Has all life descended from a common ancestor?
The evidence for a "yes" answer to the above is overwhelming. Not least, because, having elucidated the basics of inheritance, scientists are in a position to know what patterns would appear in the genes of living organisms, if common descent with modification was in operation, and what patterns would appear if this mechanism were not in operation. The evidence is conclusive - common descent with modification unifies the entire biosphere. The patterns expected to appear as a result of this mechanism have been found right across the biosphere, in everything from single-celled amoebae to primates. Denial of the validity of this evidence is not only untenable, but farcical.
[5] Is it reasonable to believe the Bible?
No. This book contains hilarious absurdities, that could only have been written by people who were woefully ignorant of, for example, basic biology. A classic example being the nonsense contained in Gen 30:37-39, which asserts that it is possible to induce large scale changes in the genomes of living organisms, by the faintly ridiculous process of having the parent animals mate alongside different coloured sticks. An Austrian monk demonstrated that this was nonsense, by providing an empirical determination of the real mechanisms underlying inheritance. I direct the interested reader to look up "Gregor Mendel".
