Yes, it is a direct replacement but much faster and more reliable.
Yes. If the existing one is a SATA interface(not an mSATA or otherwise). This one uses the same connection interface. Hence compatible.
Is this compatible as a direct replacement for 2.5inch 240GB SATA 5400rpm?
I got this BX500 240GB recently from Crucial for £37 and it works well, it's a cacheless design I believe but in day to day use there's no obvious difference to a cached SSD. If you regularly shift large files then maybe look at the MX500 or a Samsung.... but this is an excellent price for a good brand SSD. There's 3.15% cashback via TCB too. I see Amazon have price matched this too.
basic SSD drives like this can often be found for less - £28 here: - https://www.ebuyer.com/858273-integral-240gb-v-series-v2-ssd-inssd240gs625v2?utm_medium=referral&utm_source=pricespy&utm_campaign=pcomp - https://www.mymemory.co.uk/integral-240gb-v-series-sata-iii-ssd-drive-500mb-s-version-2.html?wgu=711_109047_15439524194714_9fc2986576&wgexpiry=1551728419&source=Webgain