Section 138 negotiable instrument 1881

Yes, mismatch or incomplete of drawers  signature  falls under purview of sec 138 of N .I. Act. 

Yes, an illegible signature on a NI does not automatically invalidate it under the NI 1881. However, if the identity of the signatory cannot be verified, it may lead to dishonor under section 138, as upheld in Laxmikant Dyechem V. State of Gujrat (2012). The presumption of validity under section 118 applies, but practical enforceability depends on verification. 

you cannot file a cheque bounce case under Section 138 of the Negotiable Instruments Act if the cheque is dishonored solely because the signature is illegible or incomplete, as this doesn't constitute a failure due to insufficient funds. 

Yes,  it comes under Ni act.