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Because you couldn't have access to your money in the bank for 2-3 days is not a valid reason for you to use your emergency fund to invest in Bitcoin. An emergency fund is meant to solve your unexpected problems and not to be used to invest in Bitcoin, even though you intend to replace it by the time you have access to your money.
Why not, especially if you see there is a good opportunity to accumulate. You can replace it with the same amount once you can access the bank, it is a legal thing to do although you need to take a few things into consideration. In such cases, don't be too rigid in your plan and you may need to make a more flexible approach to make your investment experience better.
It would be better to make use of your reserve fund to invest in Bitcoin because if an unexpected problem happens, you can still solve it with your emergency fund. What if an unexpected problem occurs before you replace your emergency fund? Which fund would you use to solve it? You will have no choice but to sell your bitcoin investment to solve your unexpected problem. Since you are investing in Bitcoin for the long term, there's no need to be in a hurry to accumulate Bitcoin. If you couldn't have access to your money in the bank for 2-3 days, don't use your emergency fund to invest in bitcoin; wait until you have access to your money in the bank before you invest in bitcoin so that you will be on a safer side to solve any unexpected problem that may happen within the 2-3 days you couldn't have access to your money.
I don't really like your investment approach and I don't think this is a good form of discipline in investing. You must be prepared to bear all forms of risk regarding your investments and any other decisions in making budget planning, but it is never wrong if one day you use emergency fund to buy on dip when you have a way to replace them in a few days. Even if you encounter unexpected problem, you can resell the bitcoin you previously bought on the dip in the same amount. It's good to have financial discipline in sticking to a plan, but I wouldn't be that strict especially if I was only using 10% to 30% of my emergency fund.