Q4
The services you mention are particular to the UK when operating outside of controlled airspace. It is a good idea to understand them as the service you get will affect the type of deconfliction and terrain separation available.
You can find the UK R/T manual here
CAP413: Radiotelephony Manual | Publications | About the CAA. The chapter you need is the one for Commercial Pilots. This is fully compliant with the latest amendments to ICAO Annex 10.
When departing on a SID there are many routes which are coordinated between several airfields. So there is a box of airspace you will fly through. As long as you are above a certain height at a certain point you will be clear of traffic below but you can continue an efficient climb profile so long as you do not exceed the maximum height. Allowing aircraft to be between 2 heights at a particular point allows for efficient continuous climb profiles without step climbs.
I hope this is helpful.
MM