a lot of us tend to forget that the Kaveri engine was actually orginially not planned to begin with for the LCA Tejas, the first engine planned was the F404-GE-F2J3 and was highly successful, however the manufacturer, General Electric, declined for India to obtain a production agreement, so India's GTRE teamed up with France's SNECMA to develop the "indigenious" Kaveri engine.
the main reasons for the delays/partial cancellation of the K-Engine is because of this
1. ab-initio development of state of the art gas turbine tech
2. technical/technological complexities
3.Lack of availability of critical equipment & materials and denial of technologies by the technologically advanced countries.
4. Lack of availability of test facilities in the country necessitating testing abroad.
5. Non availability of skilled/technically specialized manpower
However, with the success of the sell of 36 Rafales, France is planning on spending
€1 billion on developing the Kaveri engine.
moving on from that, their missile tech was mostly provided by the Russians, most rumours indicate that the Russians provided them technology from either the Topol or Topol-M (not sure if it's true but that's what is debated), and that's why they are so advanced, the foreign aid, if they done by themselves they'd still be lagging behind.