What is the best name for this molecule? Explain your naming process.

CH3 -CH2-Ch2 C|||

CH3-CH-C

CH3

for compound CH3 it is named methyl or methyl, for compound CH3 -CH2-Ch2 C ||| since it is an alkyne for the triple bond that is why it is a group of carbons called propyne, on the other hand the last equation where CH3-CH-C is expressed, I think you meant CH3-CH-CH2 || with which this last serious propene since the double bond is what makes it an alkene.

Explanation:

The compound CH3-CH-C was considered poorly written since a carbon can always bind four hydrogens, so if the molecule is CH3 it is because it has 3 available bonds to bind with the hydrogens and one with an R (radical) If the molecule is CH2, it is because it is linked to two radicals on each side and it only has two available bonds for hydrogens or because it has a double bond, on the other hand, in the case that it is CH or it has a triple bond or is attached to three other radicals / carbons and only one bond is available for bonding with hydrogen-

It is important to understand that if a carbon in an organic chemical sequence is only expressed as C, it is because its four unions are occupied and cannot bind to hydrogens, thus being the opposite case of methane, which is CH4 where ALL ITS UNIONS ARE WITH HYDROGENS SINCE IT IS NOT JOINED TO ANY RADICAL.

Organic chemistry is difficult, I hope the equations you wrote are well expressed, otherwise if you have doubts you can consult me.