What are the pillars of prayer, and is it obligatory to say "Bismillah" before reciting Al-Fatiha and the surah that follows it and to conclude with "صدق الله العظيم" (Allah the Almighty has spoken the truth)? And is "التحيات لله والصلوات" (All compliments and prayers are for Allah) a verse or a supplication?

Prayer is a great pillar, and abandoning it out of denial is disbelief by consensus, while abandoning it out of negligence is a matter of dispute. All missed prayers, whether intentional or accidental, must be made up. The Basmalah (Bismillah ar-Rahman ar-Rahim) belongs before Al-Fatiha, and saying "Sadaqallahul Azeem" (Allah the Almighty has spoken the truth) is not prescribed in prayer. The supplication of the Adhan is recited after repeating it, not during the prayer.