A few ranked questions! (I'm pretty new to ranked.)

Hiya! c:

I started playing ranked just this week and I had a few questions I can't find a proper answer to, if anyone could answer them or confirm anything I say it'd be a great help! So I played my first 10 provisional games in a week, won 7/10 and was given silver rank, divsion 1! I was actually quite excited and never thought i'd get that high after winning only 7 games with average scores (three I carried). I've been dying to get to gold rank, even if it's gold 5! So here are my questions;

1. How many games roughly would I need to win (if ranking up is based on wins) to get to gold 5?
2. How does the ranking system work exactly when ranking up divisions?
3. How do I get demoted exactly? (I know we all lose games but I'm so worried of being demoted lol.)
4. If I were to get to gold, would I decay back to silver if I didn't play or is that just Platinum and above that decay?
5. Can gold 5 recieve the victorious skins? (I heard you have to be like gold 1 - 3 to get them?)
6. And since I'm a noob to playing ranked, could someone please explain what LPS and MMR is?

Any ranked tips would also be lovely if you have any n . n Thanks to anyone who can help!