54D MMM on 2320R lift knob question

Hello,

I am a new tractor owner. Our 2320R was delivered yesterday. We did not order the independent lift (hydraulic) as the dealer said it had a mechanical lock to separate it from the 3PTH when using a rear implement. The height adjustment knob on the floor for adjusting blade has a lock icon, which I assume is to lock the MMM up when in transport or using a 3 PT hitch implement independently.

Here are my questions:
1. Does the 3PTH control stick have to be any particular position (1-9) to lock the MMM up with the blade adjustment knob?
2. Is it okay to use the MMM if it is locked up?

Any additional advice regarding this set-up would be appreciated.

Thank you,
peffleyjeanne