How to control my CH thermostats please

[Sabatinitennis]

Just moved into a four-bed, five year old house in Glos.
There is a Worcester Greenstar boiler in kitchen on the ground floor.
On a ground floor hallway wall is a Honeywell CM 907 thermostat which has too many buttons and programmes and a second one on the wall of the first-floor main bedroom and, seemingly, a third thermostat in the airing cupboard which houses the large water tank on the first floor.
All radiators excrpt two have thermostats on, so I cannot turn down the excessive heat that the main bedroom radiator emits.
Ok ..questions ...(1) can ALL radiators be fitted with thermostats? ....
(2)if I turn all the radiators down will the boiler blow up as the heated water has nowhere to go?
(3) If I go on holiday and want to turn the boiler off ...which of the three thermostats do I turn off? Is one a dominant one?

 

[muggles]

1) Bit of a debating point but I say yes, provided there's a suitable bypass in place to maintain a minimum flow rate through the boiler.

2) No

3) All of them. They will all have equal priority

 

[Sabatinitennis]

Thank-you