I probably cannot answer all the questions, but will try.

I usually use wet 10% Pd/C, although other species can be utilized; the success of the reaction depends more on the substrate specificity and reaction conditions. Alcohols are typical as solvents, both for H2 or ammonium formate as hydrogen donors (I prefer catalytic transfer procedure with ammonium formate for the simplicity of the procedure).

The state of Pd is not important - it is supposed to be Pd metal, but even if it is partially oxidized, it will be reduced to Pd(0) quickly under the reaction conditions.

I never bothered recycling the catalyst, so no comments on this.

Deactivation of the catalyst usually happened when your substrate contains phosphorous, sulfur or similar impurities; if your substrate molecule itself contains S or P in it, then deprotection could be very slow or impossible at all.

Catalysts like Pd on Al2O3 of CaCO3 might work, but usually they has much less surface area comparing to similar Pd/C catalyst, and this could make the reaction to proceed slower.

I probably cannot answer all the questions, but will try.

I usually use wet 10% Pd/C, although other species can be utilized; the success of the reaction depends more on the substrate specificity and reaction conditions. Alcohols are typical as solvents, both for H2 or ammonium formate as hydrogen donors (I prefer catalytic transfer procedure with ammonium formate for the simplicity of the procedure).

The state of Pd is not important - it is supposed to be Pd metal, but even if it is partially oxidized, it will be reduced to Pd(0) quickly under the reaction conditions.

I never bothered recycling the catalyst, so no comments on this.

Deactivation of the catalyst usually happened when your substrate contains phosphorous, sulfur or similar impurities; if your substrate molecule itself contains S or P in it, then deprotection could be very slow or impossible at all.

Catalysts like Pd on Al2O3 of CaCO3 might work, but usually they has much less surface area comparing to similar Pd/C catalyst, and this could make the reaction to proceed slower.

Vladimir answered pretty well, I'll just add:

1- We had 5% Pd/C, and it worked fine. If it is sluggish, the catalyst can be activated by heating it in vacuum for a while.

2-The Pd/C contains a mixture of Pd, including some in nano states, it is not usually well defined but it does the job. I think prof. Annanikov had a paper on this...

3-Pd/C is rarely recycled in academic labs, so I can't comment. In theory, if you have a good filtering system, you might recover some of it...

4-Deactivation is a risk with heteroatoms. If you are deprotecting a nitrogen, I highly recommend working in acidic conditions to deactivate the free amines (MeOH/AcOH system).

5- already answered.

We can use 10% Pd/C with MeOH/EtOH as a solvent or Pd(OAc)2 also you can use, that will depends on the reactent.