OK as no one else has had a go -
Don’t take this the wrong way but clearly you are at the start of the learning curve and there is lots you need to get your head around. I'll keep the answers short and try to be on point, that isn’t the same ad being terse, just don’t want to write a book.
1/ Not really, depending on lots of variables you might be mashing in any ware from 2:1 to 6:1 (always L:G Liquor being a name for brewing water Grist is your grain). Low L:G favours protein and glucan breakdown, higher L:G favours Amylase (starch degrading and sugar forming enzymes). You tend to get better efficiency at higher L:G and a more delicate beer.
The size of your grain bill and your mash tun or the grain capacity of your malt pipe will all play a role in choosing the ideal L:G
If you are doing long slow sparges, mashing in somewhere between 3&4:1 is probably a good place to start. if you arent sparging slowly a higher L:G will get you a better yield.
2/ 60m at 67oC is a pretty common option it’s a compromise between the best temperatures for Alpha and Beta Amylase, a little cooler (63-64oC) will give slightly dryer and more alcoholic beer, reverce for slightly warmer (66-68oC) gives fuller flavoured lower alcohol beer.
There are lots of good reasons to step mash (mash at various temperatures) if you can it will give more yield and more control over the flavour of the beer.
It would help if we knew what you were brewing on equipment wise.
3/ 73oC would barely be regarded as a mash out. The point of a mash out is twofold, first to end all enzyme activity, second to make the sugary wort as fluid as possible.
There are problems with getting the mash hotter than 80oC, mainly with Tannins extracting from the husks and giving the beer a harsh flavour.
Generally just under 80oC is ideal, acidifying your sparge water helps prevent tannin extraction to.
4/ Lots happens in the boil, it is really one of the most important and least regarded steps in the brewing process.
I know you will hear lots of contrary opinions but I would regard 60 minutes as a minimum for most beers and 90 minutes as a better option.
Don’t stop boiling based on volume, if you need to, top up your boil with water to keep your target volume. The boil time will affect the pH of the wort, the flavour, the colour how much bitterness you get from your hops and a bunch of other variables that will have a real effect on your beer. Best not to screw around with your planed boil time too much. This is one place where a refractometer is really handy, you canget an accurate gravity reading with just a couple of drops and pretty much instantly.
Yeast is so personal that many recipes will just leave it up to the brewer, it’s worth familiarising yourself with the difference between Ale and Lager brewing (stick to Ale until you have the basics right).
Even within the Ale family there are lots of options, again read up on them and see which sounds like it’s worth a go. US-05 is the best selling dry yeast, far from my personal favourite but it’s useful for some styles. Nottingham is well worth a try as are many others, have a look at the beer you are brewing and maybe Google the style and see what others are using.
I'm not a fan of pressure fermentation, if you apply pressure early you will suppress a lot of the flavours the yeast brings to the beer, in many styles these are a vital parts of the style.
No problem with closing up the fermenter late in the brew to build up condition (fizz) and/or using that pressure to push the beer into a keg...
Good temperature control is far more important than spending money on pressure gear.
If you want to dig into any of this deeper, ask, but please do inform as to what you are brewing on, that will help a heap.
Mark
Posted many times before but wort reading.
