This contains links to other posts, all worth a read.
Basically the assessors vary, some are great and understand autism and score accordingly, others don't. Some mums in your position have no difficulty at all, others have to fight their dc's corner and take their case to Tribunal.
Get a copy of your assessor's report in any case, then if you need to appeal, go for it. Over 70% of No decisions are overturned at Tribunal.
If s/he can't do something, never answer their question with yes, but, because it can be recorded that you said he can do it, always answer with No, but then qualify your statement.
Questions you'll be asked are about daily living and about getting around. Short physical 'exam' to demonstrate movement like standing, bending, raising arms above head etc.
e'g' raising arms = physically capable of xyz tasks will be recorded in the assessor's report.
Good Luck!