Re-create 15s Timeframe "candle by seconds" EA and calculate ema

Hello,
i have a few steps to this EA for mt5

1 ) The first step is to recreate the exact function of this FREE EA "Candle by Seconds"  https://www.mql5.com/en/market/product/51159?source=Site+Profile
i need to have the same candle output on EURUSD 15s, including  "Reproduce the history of the last 5 days from the date it was inserted in the chart". But it only needs to load enough history data to be able to calculate the ema from step 2

The above step is needed to prove that your code does create the exact same candles as the existing "candle by seconds EA" how you prove that it creates the same candle output is up to you.

2 ) Second step:

But instead of opening a new separate window i need this EA to run on the 1minute window, EURUSD, MT5. And create the 15s timeframe in the background. No visualization needed. The 15s candles only need to exist in an array/buffer.
Then calculate one EMA over the 15s close. No visualization of this EMA is needed.

3) third step: When the ema crossed a value it will:
if positive crossover condition is true: close all sell positions and add a buy position
if negative crossover condition is true: close all buy positions and add a sell position
it continues to trade over the weekend and overnight

4) fourth step: i want to use this EA to also use it in the MT5  strategy tester to backtest my strategy on the 1m timeframe window. but then actually make trades based on the 15seconds.

Configurable inputs:

1-60 seconds must be configurable
ema length must be configurable
crossover(EG 1.556677) crossunder(EG -1.556677) value must be configurable

Of course i need the source code.

Thanks

Looking forward to the replies. Please let me know if all my steps are possible and how you propose to tackle the problems