1a and 1b are both correct. Their suggestion is slightly different. 1a - the word 'will' must be stressed. It means if you insist on doing this. If you WILL ... is means the person continues with behaviour even though it is bad, unhealthy, annoying, etc. e.g. If you WILL smoke, please do it outside. If 'will' is not stressed, this will sound strange and incorrect. 1b just means this action will have this result. There is no judgement suggested. 2a and 2b are both correct. Again, they have a very slightly different suggestion. If you will wait here = If you agree to wait here. It's polite. If you wait here = no suggestion of 'agree'. It is not impolite. 2c makes little sense in that there is obvious reason to say something like this.