The correct height rings you need for a Vortex Diamondback 4-16x42mm Scope you depend on the rifle and base you are mounting it to. The Vortex Diamondback 4-16x42mm scope has an objective lens outside diameter of 2.0" so you will want a set of 1" diameter rings with a centerline height of around 1" for most bolt action rifles. The guide below will help determine what ring height your need.
https://www.opticsplanet.com/howto/how-to-how-to-measure-scope-height-scope-ring-height.html
The 1.12" SIG SAUER Alpha Aluminium Hunting Rifle Scope Rings will provide enough clearance of your objective lens on your Vanguard rifle. MPN:SOA10021.
For that scope I recommend using the SIG SAUER Alpha Aluminium Hunting Rifle Scope Rings 1" diameter 1.12" high set.
I recommend using the 1" diameter .94" height SIG SAUER Alpha Aluminium Hunting Rifle Scope Rings for that scope. However, I recommend also using the picatinny base for your rifle at the link below.
https://www.opticsplanet.com/christensen-arms-one-piece-scope-base.html?_iv_parent-gun-make=remington
Yes, the 1.25" 30mm SIG SAUER Alpha Aluminium Hunting Rifle Scope Rings will be compatible with your Sierra3BDX 4.5-14x 50mm riflescope and Sig Cross rifle.
I would recommend using 1.25" height SIG SAUER Alpha Aluminum Hunting Rifle Scope Rings in order to allow for clearance of your objective lens.
The 0.94" Sig Sauer Alpha Aluminium Hunting Rifle Scope Rings will be able to accommodate an objective lens up to 44mm. So any of the 0.94" will work with your scope and rifle setup.
This depends on a couple of things but mainly the tube diameter of your scope. I would get medium or high height rings either in 1 inch or 30mm depending on the diameter of your main tube. You can also use this how to guide to help with your selection.
https://www.opticsplanet.com/howto/how-to-how-to-measure-scope-height-scope-ring-height.html
This depends on the type of base but the lowest 1 inch Sig Sauer Alpha Aluminium Hunting Riflescope Rings you could most likely use would be the 0.85 inch high model.
I would use the 1 inch 0.85 inch high Sig Sauer Alpha Aluminium Hunting Riflescope Rings.