The only purpose of an earmarked reserve is to identify that funding is being saved for a future project. As a general rule, an earmarked reserve is created or amended at the end of a financial year to carry forward to the next year not because it can't be spent for 12 months but because timescales for the project mean at the end of the financial year, the project hasn't been completed (or even started!). For example, last year my council received a grant for some play equipment and the grant was received in advance of the order being placed (and goods received) so reserves carried forward (i.e. money in the bank) were increased by the amount of the grant at the end of the financial year because the grant had been received just before the FY end. An earmarked reserve was created to identify to the public (and auditors) that the money was being held in the bank account for a specific purpose. In due course, the play equipment was purchased and the accounts at the end of the next financial year will reflect that the EMR will have been reduced accordingly.
Earmarked reserves are not separate funds that have separate financial regulations. Expenditure from an earmarked reserve is the same as any expenditure, requiring the same procedures for quotes, etc. If a committee has authority to spend it is exactly the same procedure whether that expenditure is from the precept, general reserve or earmarked reserve.
Expenditure against all budget headings should be reviewed during the financial year and ideally at every meeting so everyone can see what has been spent against all budget headings, what remains and where there might be issues of over expenditure that need addressing.