Julio, words like greetings or terms of address that don't carry specific _meaning_ and are said as a sing of something, they often are contracted in speech. In the case of пожалуйста there are two reasons: 1) it is HARD for a Russian to say -йст-. 2) Russians forgot the etymology. Centuries ago it was пожалуй+ста (and both parts had meanings). That were two words basically. Now Russian has lost the particle -ста. Similarly we don't say the first в in здра[в]ствуй. -вств- is hard to say:( But we say в in "до свидания"! You're mistaken. At least I do:) Maybe we just say it fast

A lot of letters are muted in French and English words... So there could be some in Russian too. In the word "свидание" you need to pronounce all the letters.

Actually, it wouldn't a mistake at all if you do pronounce Й in russian words. If Russian speaks slowly enough you can hear Й. And the sound is reduced when you speak faster. So you can pronounce it without any doubt. As for the "СВИДАНИЕ": yes, "В" is pronounced in this word. And usually, it sounds quite distinct.

Thanks so much

listen to this audio to pronounce пожалуйста and до свидания https://vocaroo.com/i/s1dMty7sz2vL