First and foremost make sure you do have a research first before asking this so you'll have a basic knowledge also. My answer is here.
1. This wallets don't let you export any private keys of this wallet. Because accessing private keys are the only way you can full control your wallet. Differences mentioned already, and Why only this x wallet do and not others? They have their reasons, you ask their developer/team why they do that, I'm just a user too.
2. Because they not fully secured wallet, blockchain listed on bitcoin.org but they removed it when there's a hacked of their wallet few years ago. And jaxx is a multi wallet and too many bugs, and I don't know the other one.
3 and 4. Don't compare the apps in bitcoin.org and bitcoin.com they have their own point of view and they have different admins behind that site. Remote apps means developers of this wallet can remotedly control your coins, so you need to trust them when you use this wallets, vulnerable evironment are wallet that are vulnerable to malware and of course the opposite is not.
Even you can see in some site that this x wallets that are secured but if you are careless using it then its the same thing from unsecured wallet.. And please do your own research first before asking, mostly of those question of yours are totally answered already. And for your more information web wallets are not totally safe because they can be taken down anytime and when the servers are down like their site then theres no way you can use that wallet or send your coins to anyone Unless you fully control the wallet like mentioned above.
bL4nkcode, thank you for your help.
So which online/web wallet gives full control (private key access) and is most secure/trusted?
Thanks.
Coin.space is definitely not the only one, i'm not sure why bitcoin.org hasn't got others listed.
A very obvious example that comes to mind would be blockchain.info, even though they recently removed the "export private key" functionality which was initially the easiest way to get your privkey, you are able to use the 12 word mnemonic to recovery your wallet and extract the contents of your wallet using any BIP39 supported wallet. There are also chrome extensions you can get which you control your private keys as well, like Jaxx and whatnot. But these are even less secure than blockchain.info etc.
Honestly shared wallets like Bitgo and btc.com are fine too, except i would recommend not storing anything over 0.1 BTC with them.
If you are storing anything over 0.5 BTC make sure you use desktop clients instead. Copay, electrum make the process so much simpler.