Can I be denied entry into the Philippines due to a past felony conviction?

Let me ask you have you commited the felony in USA or in the Philippines. If it was in the Philippines you will not be denied entry instead you will be arrested and put to jail. But if you have serve the sentence then there's nothing to fear about being denied. But if it happened in the USA or other foreign country then it would be based on Philippine Laws concerning convicts from other countries about to enter Philippine soil, in coordination with the country of origin from which you are a citizen. then you have to pass the proper channels the Philippine Consulate to test whether you will be granted entry or be denied. I think thats it, its the very basic element of the whole process ask for a visa.

if you do not admit to a past conviction when applying for a visa, you will be ok, i promise you, 100% sure.

Yes, absolutely.

Only if it's for stealing shoes.