Student or Learner
Is it ok to say "You have to take your hand as much back as possible"?
Always capitalise 'OK'.
Move your hand as far back as possible.
'as far back as...' is what you want. Interesting point though; I wonder why 'as much back' doesn't work here; I imagine students would find a 'rule' useful... I'd suggest this: 'as much' only works if it's not followed by a preposition.... But that doesn't cover things like 'Our object is give as much back as we take out.' Maybe the 'not before a preposition' rule would work if it had an exception for this sort of 'pronominal' use of 'as much' [where it means 'as much joy/food/money...']. Hmm... not very elegant...
OK so we cannot use "Much" here.