Basicity comparison of ammonia derivatives (and guanidine) Arrange the following in decreasing order of basicity:
  
  
  $\ce{N(CH3)3}$
  Guanidine
  $\ce{N(C6H5)3}$
  $\ce{NH(CH3)2}$
  


My answer - 2 > 1 > 4 > 3

Option '2' due to equivalent resonance structures on protonation. Then option 
 '1' due to thrice +I effect. Followed by option '4' having +I effect twice which causes the lone pair electrons to be repelled from the nitrogen atom. Finally option '3', because lone pair electrons are delocalised on three rings.

Is my logic for the question correct or not? I am not sure if my answer is correct.
In triphenyl amine (3), the lone pair of nitrogen is in conjugation with phenyl groups and thus would be least available for protonation.

Due to resonance structures of guanidine (2), it should be the strongest base.

Although number 4 doesn't exist as it is written. Let's suppose it is $\ce{N(CH3)2}$ with a negative charge (the only possible way to have two methyl groups on a nitrogen).

If so, it is more basic than guanidine, because charged compounds are generally more reactive than neutral ones and will attract $\ce{H+}$ more quickly.

So if number 4 is charged, then the basicity will decrease in order
4 > 2 > 1 > 3