Is it true that everything you do on the web such as web browsing and reading email you can do with Telnet?
Yes, although that would forfeit benefits of compression, and working with chunked GET response or Base64-encoded login/password in SMTP would be painful, so I wouldn't recommend actually using it except for testing purposes, use Perl or python if you want to do something on the web automatically.
Also, if you want to make requests that are indistinguishable from the ones a certain browser makes (having to do this is a sad reality when you're trying to work with sites protected by systems such as Bad Behavior), consider writing a mini-server that will output your request verbatim (there are such examples flying around, but they will probably need some slight modification). Then you will be able to use it as a template to make simple requests to such sites.
For example, try
When the initializing is done, type
and press ENTER twice (as required by HTTP protocol). You will get 302 response that a browser would normally use to redirect you to WWW.google.com.
Technically yes, you can do that. but pragmatically speaking the answer is no:
for example, i can get a webpage using
telnet www.page.com 80
but i will get the html text from it, not the,css, image and other resources.
Then, with the html file, you can get every other files with consecutive telnet calls. css is "trivial" to get, it is the same to get a file, also js and other "included" files. but binaries are not as easy because i must download it then process it, without counting that some resources required a specific cookie and a ref.
And the website may be is forcing for z-compression and many other "details" that are "detailed" in the specification of the protocol, protocol that is hardly patched and with several exceptions.
While is possible but it is the same to build an exist service/protocol from scratch so, it is the same to say "i can build Windows just "poking" zeroes and ones." <-- is possible but it will take a lot of absurd time to do that.
Anyways, outside web and email, exist some protocol that can't be accessed using a plain telnet because it required some kind of timely handshaking (a couple of seconds if not less) that can't be imitated using two separates call to telnet without using some sort of automatism, i.e. we are talking about a client that is not a proper telnet client but over it.
Telnet can be used for (nearly) raw TCP connections, and you can use character-based protocols with it, but there are some differences:
Otherwise, you're able to use character-based application layer protocols such as HTTP, FTP, SMTP and IRC using Telnet. Cince it's quite a challenge to read and write compressed data manually, you're limited to HTTP without HTTP/1.1's compression. For protocols that are entirely binary, you're pretty much out of luck.