1 and 3 are correct.
There are many plants in which parts like the root, stem and leaves develop into new plants under appropriate conditions. This property of vegetative propagation is used in methods such as layering or grafting to grow many plants like sugarcane, roses, or grapes for agricultural purposes. Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds. Another advantage of vegetative propagation is that all plants produced are genetically similar enough to the parent plant to have all its characteristics.

Both 1 and 2 are correct.
Phytoplanktons are the foundation of the aquatic food web, the primary producers. Zoo plankton feed on phytoplankton and play a vital role in food web of the food chain, nutrient recycling, and in transfer of organic matter from primary producers to secondary consumers like fishes.

All of the above are correct.
Sea weeds are macroscopic algae, which mean they have no differentiation of true tissues such as roots, stems and leaves.
They grow in, shallow coastal waters wherever sizable sub-strata is available.
Seaweeds are important as food for humans, feed for animals, and fertilizer for plants. Seaweeds are used as a drug for goiter treatment, intestinal and stomach disorders.
Products like agar-agar and alginates, iodine which are of commercial value, are extracted from seaweeds. By the biodegradation of seaweeds methane like economically important gases can be produced in large quantities.
They are potential indicators of pollution in coastal ecosystem, particularly heavy metal pollution due to their ability to bind and accumulate metals strongly.
Rotting seaweed is a potent source of hydrogen sulfide, a highly toxic gas.

Billions of pieces of plastic pollution are snagged on coral reefs, sending disease rates soaring, new research has revealed. The discovery compounds the damage being done to a vital habitat that already faces an existential threat from the warming caused by climate change.
Scientists examined 125,000 corals across the Asia-Pacific region, home to half the world’s reefs, and found 89% of those fouled by plastic were suffering disease.
The correlation between plastic pollution and high rates of disease was very striking and the researchers think sharp plastic fragments cut the coral organisms, while plastic fabrics smother them and block out light and oxygen. Once a coral is infected, disease usually spreads across the colony.

1 and 2 are correct.
Ecological pyramid doesn’t give evidence on introduction of new species.