“Set its value at X”. There is no nob or “setting” to do this.

There are plenty of Forex exchanges trading RUB for any currency. Including USD, EUR and others. Governments don’t have control over all exchanges so they can’t set the price. The price is determined by supply & demand (ie: the market). Governments do have some levers they can use: buying or selling reserves to put up or downward pressure on the market price.

To limit trading of a currency you’d have to limit exchanges to any other currency. If you limit RUB-USD for example, people could still trade RUB-EUR and EUR-USD, thus still creating a defacto RUB-USD pricing.

Lol. Literally just bough a flagship phone from China at a market rate price. (QIWI payment system) Ruble go up, might as well buy a 3080ti next time.

but will you be able to sell fuel and fertilizer?

USD isn't the only currency you can exchange RUB for to conduct mutually beneficial transactions.

How many ft3 of gas are you selling daily?

Can the gas coupons be used for buying consumer goods? Right now doesn't seem to be the case. Money flows one way. Since Russians don't produce anything except raw materials, high currency value doesn't matter since they can't spend it.