PF Contribution %

(1) Can the Employer and Employee Contribution % be different for any amount over and above 15000/-? Example Say if Basic is greater than 15 K at present (Say Rs.100000/-) then Employer Contribution would be 12% and Employee Contribution would be 12 % on 15K. For amount over and above i.e. on 85000/- (Rs.100000/- – Rs.15000/-), Can employer Contribution be 12 % or different and Employee Contribution % can be any other say 8% (not matching to employer contribution). In other words, will both employer and employee have to contribute @ the same % for amount over and above 15K? (2) If anybody’s Basic is more than 15000/- (Say Rs.50000/-) then why should he be covered under PF? We understand that this is applicable only in case of New Joinee, wherein if basic is more than 15 K, he can be considered as an excluded employee. Thus is it Mandatory to deduct PF is Basic is more than Rs.15K?, if yes, then can this be applied (i.e. reversal can be made) to existing employees with higher basic OR it is possible only at the time of Joining.