Which ABI to call to get the APY from the supply and borrow?

You can call getReservesData or getReserveData on the aaveProtocolDataProvider contract, on the pool, or on the UiPoolDataProvider.

These will return a lot of data including:

• currentLiquidityRate: current supply rate. Expressed in ray
• currentVariableBorrowRate: current variable borrow rate. Expressed in ray
• currentStableBorrowRate: current stable borrow rate. Expressed in ray

A ray is a unit with 27 decimals of precision. All the rates (liquidity/borrow/utilisation rates) as well as the cumulative indexes and the aTokens exchange rates are expressed in Ray.

You can call getReserveData on the Pool contract to get rates for a single asset or getReservesData on the UiPoolDataProvider contract to fetch rates for all assets at once. More details here;