How do u know that 3L52aKJdATfaNMvz8i9nvHWaY2Mvt3bVtL is a SegWit address and not a legacy MultiSig one? I mean, how to differentiate between the two?
It's not possible to tell from the address alone, you can only see it in the transaction. So if an address has never sent an output they are indistinguishable.
If they have sent an output then it's the input scripts. So from that Tx:
ScriptSig: PUSHDATA(34)[002055c79c9fabc96629070f80be73840f7de4922e80beb4ea81bda984fecb86388f]
Witness: 0400473044022023a1cb31e2c191a1bcdfee349bbabba87cdd0ba35af83b7d6a688b7591a67afa0 22075bb661dcbb2683b8467e98546d12764c54ecb5834f4a52ee67cb3826baa8b96014830450221 00d6fcf31d6113e9899d704b0f7dab796d34b8e09f6d6bc9f817e93dfa6f9f0be902207d4956581 437f0f73a3098d8184dc07712b24a3d53db362d5a696d87e73365a501475221039f54f730f54faa fdc50f28e2cea94deb4c512ccd8c63e146f0a3bbbf7ea3e56721027a900cf1bc28805f5747fd9d4 b9fd3ff8ff10c0ba15b8caba8dd750f1e22db0452ae
Whereas a MultiSig transaction like this one:
https://blockchain.info/tx/1450b72940ff3d1353fc1aa59cb5a848eeed8a5dd3549bc546f8d4965eae9443
Looks like this:
ScriptSig: 0[] PUSHDATA(72)[3045022100827e9b5b157e8d3495a0cebcc21ca90f81206b7ad9b329fc7920239ff229c0bf0
22065918b33e953870bdcdb5e789d6068f313ebd76d430a2e331ab5fc45b9ddc62c01] PUSHDATA(37)[5121030ec111fb923515ba4747f3c7005b4398e81d816a66ba50306aacac2f405ac72651ae]
