How does the russian interest rate raise will defends the Ruble from devaluation?
An interest rate is the return that a lender earns on money lent to someone else. If the interest rate is higher then it makes lending money more attractive because the return is higher.

In particular, if the interest rate in, say, Russia increases relative to that in the USA then American lenders will switch from lending their money in America to lending their money in Russia where the return is greater. But in order to lend money in Russia, these investors are first going to have to convert their dollars into roubles. This increased demand for roubles causes the price of the rouble (i.e. the exchange rate) to increase.